| 摘要 |
PURPOSE:To assure an access quickly and accurately to a desired track detached from a reproducing head and even to a different track pitch, by calculating the number of tracks which cross the reproducing head and actuating a tracking control means when the counted number of a tracks reaches a prescribed value. CONSTITUTION:The output of a reproducing head 5 is detected by an envelope wave detector 14, and a counter 18 works when the output of wave detection is larger than the reference potential V. The output of a subtractor circuit 11 is converted into a signal showing absolute value (n) through an absolute value converting circuit 19 and compared with the output of the counter 18 at a comparator 20 to deliver a low or high level. A switch circuit 15 connects the output of the detector 14 to the counter 18 and a tracking control circuit 21 with low and high levels, respectively. Therefore, a high-speed access is kept until the head 5 crosses the (m+n-1)th track, and the regular tracking control is executed at the (m+n)th track. |
